The halophilic bacteria, Vibrio parahaemolyticus and Vibrio fluvialis (formerly Group F or EF6 vibrio species), are associated with enteric disease in humans. V. parahaemolyticus is a well-established pathogen while V. fluvialis has been epidemiologically implicated as the etiologic agent in cholera-like diarrhea and has fulfilled Koch's postulates as such an agent in an animal model. The objective of the proposed research is to purify and characterize the putative enterotoxins (CHO cell elongation factors) which are produced by the two halophilic, enteric pathogens, and to evaluate the role of the toxins in the pathogenesis of enteric disease caused by the bacteria. The approach which will be taken to meet the two objectives will include: (i) determination of growth conditions optimal for toxin production, (ii) development of extraction procedures for obtaining maximal amounts of crude topin preparations, (iii) development of a purification sheme for obtaining large amounts of homogeneous toxin preparations, (iv) physicochemical, biological and serological characterization of the homogeneous toxin preparations, and comparison of the toxin's properties with those of other known enterotoxins, (v) evaluation of the efficacy using our newly developed Sealed adult Mouse (SAM) model, of active and passive immunization against the toxins in preventing or reducing the severity of experimental enteric disease by the bacteria, and (vi) studies with naturally-occurring and laboratory derived toxin deficient strains or mutants to determine if there is a correlation between the ability of the bacteria to produce the toxins and their virulence for experimental animals.